Method, apparatus and system for providing light source structures on a flexible substrate

ABSTRACT

Light emitting diode (LED) package structures employing large area substrates are described. Panel or reel-to-reel substrate processing is utilized in the manufacture of such LED package structures. In some embodiments, electrochemically deposited metal patterns and through substrate vias (TSuVs) are formed through glass substrates and/or interposers. In some embodiments, the metal deposited into the TSuVs offer high thermal conductivity a low coefficient of thermal expansion (CTE) that is to closely match the CTE of the glass. Singulated LED package structures including a plurality of LEDs arrayed for displays, such as, but not limited to, liquid crystal displays (LCDs) and LED displays or for general purpose LED light sources are described, as are LED package structures including active devices (e.g., ICs) and/or passive devices (e.g., capacitors, inductors, resistors, etc.) integrated with LEDs at the package level.

TECHNICAL FIELD

Embodiments of the present invention generally pertain to light sourcestructures employing light emitting diodes (LEDs) and more particularlypertain to LED packaging.

BACKGROUND

Currently standard LED packages offer limited integration andfunctionality of light source systems and do not extensively integratepassive and/or active components at the package level. One reason forthis is that system cost increases considerably and devices integratedwith the LEDs suffer from large thermal cross-talk that reduces devicereliability. The high cost of integration is, in part, attributable tocomplicated package structure and reliance on relatively expensivepackage substrates.

FIG. 1 illustrates a conventional LED package structure as formed by aconventional packaging method 100. LEDs 105 are disposed on a siliconsubstrate 110. The silicon substrate is typically a wafer of the typeemployed in integrated circuit manufacture. As such, the substrate areais limited to the state of the art in IC manufacture, which is currently300 mm diameter wafers. While 450 mm diameter wafers are in development,no further increases in silicon wafer size are expected in the comingdecades due to prohibitively high tooling costs. With the area of thesubstrate 110 so limited, many substrates are required to manufacturehigh volumes the conventional LED package structure. Also, to fabricatea matrix or array of LED devices into a form factor that is larger thana conventional silicon wafer, such as for a large panel display screen,or high lux light source, wafer substrates must first be cut intosquares or completely singulated and then re-assembled with like unitsinto a large matrix.

As shown in FIG. 1, the packaging method 100 entails forming a cavity115 in the silicon substrate (e.g., by a KOH etch) and depositing ametal film 120 in the cavity. Through substrate vias (TSuVs) 125 arethen formed and the LED chips 105 are mounted with a chip to wafer (C2W)bonding process. A silicone encapsulant 130 fills in the cavity 115 anda lens wafer 135 is bonded with a wafer-to-wafer (W2W) bonding process.Singulation is then performed to arrive at packaged LED structures.

An LED package structure that enables larger form factors with reducedassembly, enables less costly package-level integration with activeand/or passive components, offers improved thermal management, and allat a reduced cost is therefore of significant technical and commercialadvantage.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not limitation, in the figures of the accompanying drawings inwhich:

FIG. 1 illustrates a conventional LED package structure and fabricationmethod;

FIGS. 2A, 2B, 2C and 2D each illustrate a cross-sectional view of an LEDpackage structure, in accordance with an embodiment of the presentinvention;

FIGS. 3A, 3B, 3C, 3D, 3E, and 3F each illustrate a cross-sectional viewof an LED package structure, in accordance with an embodiment of thepresent invention;

FIG. 4A illustrates an LED bulb, in accordance with an embodiment of thepresent invention;

FIG. 4B illustrates a cross-sectional view of an LCD display employingan LED package structure, in accordance with an embodiment of thepresent invention;

FIG. 4C illustrates a plan-view of an LED display employing an LEDpackage structure, in accordance with an embodiment of the presentinvention;

FIG. 4D illustrates an LED system, in accordance with an embodiment ofthe present invention;

FIGS. 5A and 5B illustrate substrate handling techniques for fabricationof LED package structures, in accordance with embodiments;

FIG. 5C illustrates a factory line for fabrication of LED packagestructures, in accordance with embodiments; and

FIG. 6 illustrates a method for fabrication of LED package structures,in accordance with embodiments.

DETAILED DESCRIPTION

In the following description, numerous details are set forth. It will beapparent, however, to one skilled in the art, that the present inventionmay be practiced without these specific details. In some instances,well-known methods and devices are shown in block diagram form, ratherthan in detail, to avoid obscuring the present invention. Referencethroughout this specification to “an embodiment” means that a particularfeature, structure, function, or characteristic described in connectionwith the embodiment is included in at least one embodiment of theinvention. Thus, the appearances of the phrase “in an embodiment” invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, structures, functions, or characteristics may becombined in any suitable manner in one or more embodiments. For example,a first embodiment may be combined with a second embodiment anywhere thetwo embodiments are not mutually exclusive.

The terms “coupled” and “connected,” along with their derivatives, maybe used herein to describe structural and functional relationshipsbetween components. It should be understood that these terms are notintended as synonyms for each other. Rather, in particular embodiments,“connected” may be used to indicate that two or more elements are indirect physical or electrical contact with each other. “Coupled” may beused to indicated that two or more elements are in either direct orindirect (with other intervening elements between them) physical orelectrical contact with each other, and/or that the two or more elementsco-operate or interact with each other (e.g., as in a cause an effectrelationship).

The terms “over,” “under,” “between,” and “on” as used herein refer to arelative position of one material layer with respect to other layers. Assuch, for example, one layer disposed over or under another layer may bedirectly in contact with the other layer or may have one or moreintervening layers. Moreover, one layer disposed between two layers maybe directly in contact with the two layers or may have one or moreintervening layers. In contrast, a first layer “on” a second layer is indirect contact with that second layer.

Light emitting diode (LED) package structures employing large areasubstrates are described. Exemplary large-area form factors include, butare not limited to, display panel substrates having an area on the orderof 100 ft² (e.g., 10G or later panel technology), reel-to-reelsubstrates having lengths on the order of kilometers, and solar panelsubstrates having an area that is 2-10 times larger than those employedin integrated circuit (IC) device fabrication. In some embodiments,electrochemically deposited metal patterns and through substrate vias(TSuVs) are formed in glass substrates and/or interposers. In someembodiments, the metal deposited into the TSuVs offer high thermalconductivity a low coefficient of thermal expansion (CTE) that is toclosely match the CTE of glass.

In embodiments, singulated LED package structures include a plurality ofLEDs arrayed for displays, such as, but not limited to, liquid crystaldisplays (LCDs) and LED displays or for general purpose LED lightsources (i.e., bulbs). LED package structures including active devices(e.g., ICs) and/or passive devices (e.g., capacitors, inductors,resistors, etc.) integrated with LEDs at the package level are alsodescribed. For certain such embodiments, integration conventionallyrelegated to a printed circuit board (PCB) is performed directly on thesubstrate upon which the LED is mounted, thereby eliminating any needfor a PCB. In embodiments, LED package structures include one or moreICs for networking the packaged LED with external devices, such as smartphones, computers, television displays, etc., for example to support adirect addressing of the integrated LED package.

Equipment and techniques for fabricating LED package structures are alsodescribed. In embodiments, operational sequences, some of which include,selective photo-electrochemical and chemical metal depositiontechniques, are described for large panel and/or reel-to-reel (R2R)formats.

Generally, the embodiments described herein may employ any LED devicetechnology. Many LED device structures are known, and embodiments of thepresent invention are not limited with respect to such LED devicestructures. For example, any inorganic semiconductor-based LEDtechnologies known in the art, such as, but not limited to, group IV(e.g., Si) devices and group III-nitride (e.g., GaN) devices may beemployed in the practice of the embodiments described herein.

FIGS. 2A, 2B, and 2C each illustrate a cross-sectional view of an LEDpackage structure, in accordance with embodiments of the presentinvention. FIGS. 3A, 3B, 3C, 3D, 3E, and 3F each also illustrate across-sectional view of an LED package structure, in accordance withembodiments of the present invention. Generally, these illustratedembodiments exemplify how a large area substrate, such as a panel orreel-rolled material may be utilized in an LED package structure toreduce the cost of the LED package or a system incorporating such apackage. As used herein, a “large” area substrate is one which is atleast twice the area of a substrate employed in traditional ICfabrication and may be as much as an order of magnitude, or more,larger. With current IC fabrication being on 300 mm diameter substrateswith 450 mm diameter substrates in development, the surface area of anIC substrate is no more than 1600 cm². Embodiments described herein areapplicable to substrates having a surface area of at least 3500 cm² andpreferably on the order of square meters for panel embodiments (e.g., a10G LCD panel is about 3.0 m on a side), and many tens of square metersfor reel-rolled embodiments (e.g., which may be one the order of a meterwide and kilometers long).

In one embodiment illustrated by FIG. 2A, an LED package 201 includes anLED device 208 affixed to a first side of an optically transparentdielectric material 205. The LED device 208 may be affixed by anysurface mount or flip-chip bonding material. In specific embodiments alow CTE metal material is utilized as the bonding material, such as, butnot limited to, solder (e.g., SnAg, InAu) with any of: nickel-tungstenalloy (NiW), or a nickel-molybdenum alloy (NiMo), a cobalt-tungstenalloy (CoW), or cobalt-molybdenum alloy (CoMo), titanium tungsten (TiW),tungsten (W) or Covar. The LED device 208 may be affixed to a planarsurface of the dielectric material 205 where the thickness of thedielectric material 205 is minimized (e.g., less than 200 μm) or withina recess or cavity (e.g., similar to the recess 130 illustrated inFIG. 1) formed in the dielectric material 205. As described furtherherein, such cavities can be provided as part of a through substratevia, for example, where the dielectric material 205 has a thickness ofat least 250 μm. The transparent dielectric material 205 is transparentto at least one wavelength of light emitted by the LED device 208 andmay be transparent to all emitted wavelengths. Also disposed on thefirst side of the dielectric material 205 is a pair of metal pads or LEDdevice interconnects 215 that are electrically coupled to individual LEDdevice terminals 216. In the exemplary embodiment illustrated by FIG.2A, the LED device terminals 216 are disposed on a side of the LEDdevice opposite that which is affixed to the dielectric material 205,and so are electrically coupled by bond wires 220 in a surface mountimplementation. However, in alternate embodiments where the LED deviceterminals 216 are disposed on the side of the LED device that is affixedto the dielectric material 205, as in a flip-chip implementation (notdepicted), the device terminals 216 are directly bonded to metal padsthat are the functional equivalent of the LED device interconnects 215.Disposed over the first side of the dielectric material 205 is anoptically transparent cap 230 encapsulating the LED device 208. Oppositethe LED device 208, a metal film 209 is disposed on a second side of thedielectric material 205. The metal film 209 is to be reflective (i.e., amirror) of at least one wavelength of light emitted by the LED device208 and may be reflective of all wavelengths emitted by the LED device208.

For the LED package 201, the transparent dielectric material 205 servesas the substrate, and further may provide at least one of electrical andthermal isolation between adjacent LED devices 208. In embodiments, thedielectric material 205 is a silica-based glass, such as substantiallypure silica (SiO₂), non-alkali glass (of the types employed in liquidcrystal display manufacture), or soda-lime glass (e.g., of the typesemployed in window manufacture and the bottling industry). In otherembodiments, the dielectric material 205 is a polymer-based glass, suchas an acrylic. In certain embodiments, the dielectric material 205 is a(p-xylylene)-based polymer, such as Parylene X, or aluminum oxide(Al₂O₃).

In embodiments, the transparent dielectric material 205 is a large areasubstrate (i.e., having a surface area of at least 3500 cm², andpreferably of 80-100 ft² where the transparent dielectric material 205is panalized, and up to many tens of square meters where the transparentdielectric material 205 is rolled). As such, FIG. 2A illustrates asingle LED package 201 which is a repeating unit arrayed over thesurface the large area substrate. Depending on the embodiment, thetransparent dielectric material 205 has a thickness (i.e., z-dimensionin FIG. 2A) between 0.1 μm and 1000 μm. Within more or less of thisthickness range, depending on properties of the dielectric material 205,the material will be flexible, or of low stiffness. For example, in oneexemplary embodiment where the material 205 is a non-alkali glass havinga thickness of about 150 μm or less, the dielectric material 205 isflexible enough to be wound to/from a reel or spool.

In embodiments, the metal film 209 is a film continuously covering thesurface area on a second side of the dielectric material 205 that is atleast as large as the area over which LED device(s) 208 are disposed.Such a foil may further span an entire surface of the dielectricmaterial 205 forming a laminate substrate 210 upon which a plurality ofadjacent LED packages 201 are formed and then singulated. As the primaryfunction of the metal film 209 is as an optical minor increasing LEDdevice light output, the metal film 209 need not provide significantmechanical support to the package although it may optionally supplementthe mechanical stiffness of the dielectric material significantly. Assuch, the metal film 209 thickness may vary over a wide range. Inembodiments where the metal film 209 is not providing significantmechanical support to the pack 201, the metal film 209 has a thicknessless than 25% of the thickness of the dielectric material 205. Inspecific embodiments where the dielectric material thickness is between0.1 μm and 1000 μm, the metal film 209 has a thickness of between 0.01μm and 100 μm. The metal film 209 may generally be any foil withspecific metal film embodiments including any of: aluminum (Al),aluminum-copper alloy (AlCu), silver (Ag), silver-tungsten alloy (AgW),gold (Au), copper (Cu), chromium (Cr), a copper-silver (Cu—Ag) bi-layerstack, or nickel-copper-silver (Ni—Cu—Ag) tri-layer stack. One or moreadhesion layers may further be disposed between the metal film 209 andthe dielectric material 205, such as, but not limited to TiO₂. Infurther embodiments, silicon may be alloyed with the metal to provide asmaller CTE. For example, the metal film 209 may be an aluminum-siliconalloy (AlSi) or aluminum-silicon-copper alloy (AlSiCu).

The metal interconnects or pads 215 may be of a same or differentcomposition as that of the metal film 209. In advantageous embodiments,the pads/interconnects 215 have the same composition as the metal film209, enabling both to be formed concurrently by a single process, suchas plating. Exemplary pad compositions include at least one of aluminum(Al), silver (Ag), gold (Au), nickel (Ni), copper (Cu), silver-tungstenalloy (AgW), or copper-palladium alloy (CuPd). The pads 215 may alsocomprise a stack laminated metal stack, such as a bi-layer ofnickel-silver (Ni—Ag), nickel-gold (Ni—Au), nickel-copper (Ni—Cu),copper-silver (Cu—Ag), or a tri-layer of nickel-copper-tin (Ni—Cu—Sn) ornickel-copper-silver (Ni—Cu—Al). Just as for the metal film 209, siliconmay be added (e.g., AlSi) for reduced CTE (e.g., to match that of themetal film 209). In further embodiments, copper (Cu) is added forimproved electromigration resistance (AlSiCu).

The cap 230 may generally be any material optically transparent to atleast one wavelength of light emitted by the LED device 208. Anyplastics, epoxy resins, acrylics, silicones, and like materials known inthe art to be applicable for LED lenses may be utilized for the cap 230and embodiments of the present invention are not limited in respect tothe composition of the cap 230. Additionally, the cap 230 may also bedoped with any pigments and/or emission modifiers (e.g., phosphorus,quantum dots) known in the art for LED device encapsulants. The cap 230may have a planarized top surface, as shown in FIG. 2A, or have a lenstopology (spherical, Fresnel, etc). For planar embodiments where thedielectric material 205 is in the form of a large area panel, the cap230 may also be a panel (i.e., a second glass panel) disposed over theLED device with a conformally deposited transparent parylene sealing theLED device below the planar cap. Alternatively, the cap 230 may be awet-deposited material (e.g., spray on polymer). In embodiments, amaximum thickness of the cap 230 within each package 201 is at least asthick as the dielectric 205. For example, where the cap 230 is moldedinto a spherical lens, the thickness of the cap 230 at the lens axis isat least equal to that of the dielectric 205. In embodiments, the cap230 is continuous between adjacent packages 201, reaching a minimumthickness that either significantly increases the stiffness of thedielectric 205, or not. For example in one embodiment the minimumthickness of cap 230 is 50% or more of the thickness of the dielectric205) so that the total thickness of the package 201 in the z-dimensionis sufficient to preclude rolling onto a spool for R2R processing suchthat a roll-to-singulation process is performed whereby a rolledsubstrate (e.g., the dielectric material 205) is unrolled, the metalfilm 209 and pads 215 formed, the LED devices 208 mounted andinterconnected, the cap 230 deposited and package 201 singulated off thelarge area substrate. Alternatively, where the minimum thickness of cap230 is sufficiently small (e.g., less than 25% of the thickness of thedielectric 205), the total thickness of the package 201 in thez-dimension is sufficiently low to permit rolling packages 201 back ontoa spool for R2R processing.

In embodiments, the LED package 201 includes a plurality of LED devices208 coupled to a pair of metal pads 215, as shown in FIG. 2A. Forexample, many LED devices 208 may be interconnected in series, parallel,or made separately addressable through electrical circuit configurationsaccessible via the metal pads/interconnects 215. In one embodiment,power to each of the first plurality of LED devices 208 is routedthrough two of the metal pads/interconnects 215 which are in turn to becoupled to rails of a voltage supply, for example for a seriesconfigured multi-LED illumination source. In embodiments where LEDdevices 208 of a packaged device are separately addressable, a separatemetal pad 215 may be provided for each LED device 208, or a uniquecombination of metal pads 215 may be provided for each LED device 208(e.g., a row pad and column pad for each LED device 208). Bond wires 221may be utilized to interconnect the first plurality of LED devices 208,or electrically equivalent routing may be implemented with the samemetallization used for the metal pads 215, for example in a flip-chipimplementation.

In embodiments, an LED package structure includes one or more throughsubstrate vias (TSuVs). As shown in FIG. 2B, the LED package 202includes a TSuV 235 disposed proximate to the LED device 208. In theexemplary embodiment, the TSuV 235 has a longitudinal axis L₁ alignedwith a center of the LED. In alternative embodiments where a single TSuV235 is provided for a plurality of LEDs (e.g., a particular RGB or RGBWcluster) TSuV 235 has a longitudinal axis L₁ aligned with a center ofthe plurality. The TSuV is to function at least as a thermal via,improving thermal conduction between the LED device 208 and the secondside of the dielectric 205. In the exemplary embodiment, the TSuV 235extends between the LED device 208 and the metal film 209.

Generally the TSuV 235 may comprise a cavity formed from either or bothsides of the dielectric material 205. The TSuV 235 may be formed beforeor after the LED device 208 is mounted. In an embodiment, a blind vialanding on the metal film 209 has a straight wall (FIG. 2B) or a taperedwall as etched (e.g., anisotropic plasma) or drilled (laser ormechanical) from the LED-device side (i.e., front side). Alternatively,the TSuV 236 may have tapered walls with a neck in the center of thedielectric material 205 formed by simultaneous wet etching from bothsides of dielectric material 205. Another alternative is shown in FIG.2C, where an LED package 203 includes a TSuV 236 entailing a blind vialanding on the LED device 208. For such an embodiment, the blind via mayagain have a straight wall or tapered wall (FIG. 2C) as etched ordrilled (laser or mechanical) from the back side of the substrate priorto formation of the metal film 209, or tapers indicative of simultaneouswet etching from two opposite sides.

The TSuV 235 is filled with a via metal 240 having good thermalconductivity and a CTE that is sufficiently well matched that thermalstress-related film delamination is avoided when the LED package 202 isoperational. The via metal is also preferably platable as plating offersconsiderable cost savings over alternative via fill techniques, such asphysical vapor deposition (PVD). In one advantageous embodiment, boththe metal film 209 and the via metal 240 have a same composition and areplated concurrently with the metal film 209 being a non-sacrificialplating overburden of the via fill. In another embodiment, both themetal pad 215 and the via metal 240 have a same composition and areplated concurrently. While the choice of via metal being dependent onthe choice of dielectric material 205 from a standpoint of CTE matching,exemplary materials for via metal 240 include, but are not limited to,copper (Cu), nickel (Ni), cobalt (Co), tungsten (W), molybdenum (Mo),aluminum (Al), and their alloys. Noting that copper has a relativelyhigh CTE and so is not ideally compatible with a number of thedielectrics that may be used for the dielectric material 205, inpreferred embodiments the via metal 240 is an alloy of tungsten ormolybdenum which each have a relatively low CTE. Alloys thereof permittuning of the CTE as a function of alloy composition. In certain suchembodiments, the via metal 240 is a nickel-tungsten alloy (NiW), anickel-molybdenum alloy (NiMo), a cobalt-tungsten (CoW), orcobalt-molybdenum (CoMo).

In certain embodiments, the LED device 208 is disposed in a cavity orrecess below a top surface of the dielectric material 205. In one suchembodiment illustrated by FIG. 2D, a TSuV 235 having a center alignedwith a center of a plurality of LED devices 208 is partially filled withvia metal 240, for example by an electrolytic plating process employingthe metal film 209 as a plating electrode or with a selectiveelectroless process employing the metal film 209 as a catalytic surface.The partially filled TSuV 235 then forms a recess into which the LEDdevice(s) 208 is disposed with the LED device(s) 208 affixed to the viametal 240.

In embodiments, an LED package includes an interposer. FIGS. 3A, 3B, 3C,3D, 3E, and 3F each illustrate a cross-sectional view of an LED packagestructure, in accordance with an embodiment of the present inventionthat includes an interposer. Generally, any of the package structuresillustrated in FIGS. 2A-2C may be utilized in a package structurefurther incorporating an interposer. The interposer may function as ameans of mechanical support for a packaged structure, in which case theinterposer is provided as the large area substrate allowing thetransparent dielectric layer to be very thin (e.g., 0.1 μm or less).With addition of the interposer, the transparent dielectric 205 need notitself be in the form of a large area substrate, but instead merelyapplied to the interposer as a thin film (e.g., liquid depositeddielectric) built-up to form another laminated substrate 210. Theinterposer may further function to integrate an LED device with otherpassive (e.g., capacitors, inductors, resistors, etc.) or active devices(e.g., ICs).

As shown in FIG. 3A, an LED package 301 includes all the elementspreviously described in the context of FIGS. 2A-2C with like referencenumbers for like elements. Additionally, the LED package 301 includesthe interposer 350 disposed below, and in this particular embodiment, incontact with the metal film 209. Generally, the interposer 350 may beany of the materials described for the dielectric material 205, such as,but not limited to, non-alkali glass, soda lime glass, parylene (i.e. a(p-xylylene)-based polymer, such as Parylene X), and aluminum-oxide(Al₂O₃). For example, where the interposer 350 is a non-alkali glass theinterposer 350 is a large area substrate such as a panel (e.g., 10G orlater LDC panel glass) or reel-wound substrate in the same manner as wasdescribed for the transparent dielectric 205 in the context of LEDpackages 201, 202, and 203. In other embodiments, the interposer 350 isof amorphous silicon, polycrystalline silicon. In still otherembodiments the interposer 350 is a ceramic, such as aluminum nitride(AlN), or boronitride (BN). All of these materials are also amenable tolarge substrate areas. For example, large silicon panels (amorphous orpolycrystalline) of the type found in the solar panel industry may beemployed as the interposer 350. Depending on the material, theinterposer 350 may have a range of thickness between 100 μm and 600 μmwith those below about 150-200 μm sufficiently pliable to be wound on areel for a reel-based packaging process.

In embodiments, an LED package interposer includes an interposer TSuVsthat passes through the interposer thickness. The interposer TSuV has alongitudinal axis L₂ that is aligned with a center of the LED device 208or with a center of a plurality of LED devices (e.g., a RBG cluster,etc.). As illustrated in FIG. 3A, the interposer TSuVs 355 are disposedunder the high power LED devices 208 for thermal conduction while nointerposer TSuVs are disposed under the metal pads 215 or low powerdevices that may be further mounted onto the same interposer, as furtherdescribed elsewhere herein in reference to FIG. 3B. In the exemplaryembodiment, the interposer TSuV 355 extends between the metal film 209and a back side of the interposer 350. A least a portion of theinterposer TSuV 355 is filled with a via metal 360. As illustrated inFIG. 3A, the interposer via metal 360 extends an entire z-dimensionthickness of the interposer 350. The TSuV 355 may be formed as a blindvia from a backside of the interposer landing on the metal film 209. Themetal film 209 may then serve as either an electrode for electrolyticplating of the via metal 360 or as a catalytic surface for electrolessplating of the via metal 360. In one advantageous embodiment, the viametal 360 and the metal pads 215 are of a same composition, enabling thevia metal 360 and the metal pads 215 to be plated concurrently forimplementations where the plating is performed after the dielectricmaterial 205 is deposited on the interposer, for example through a wetdielectric deposition process (e.g., spin-on, spray-on glasses, etc.).

Generally, the via metal 360 may be any of the metals previouslydescribed for the via metal 240. As an example, the via metal 360 may beany of copper (Cu), nickel (Ni), cobalt (Co), tungsten (W), molybdenum(Mo), aluminum (Al), and their alloys. In preferred embodiments the viametal 360 is an alloy of tungsten or molybdenum which each have arelatively low CTE. Alloys thereof permit tuning of the CTE as afunction of alloy composition. In certain such embodiments, the viametal 360 is a nickel-tungsten alloy (NiW), a nickel-molybdenum alloy(NiMo), a cobalt-tungsten (CoW), or cobalt-molybdenum (CoMo).

For LED package embodiments that include an interposer, the interposermay either be bonded to either one of the metal film 209 (where themetal film 209 is not first plated onto the interposer 350) or thedielectric material 205 (where the metal film 209 is first plated ontothe interposer 350), or the both the metal film 209 and dielectricmaterial 205 may be deposited onto the interposer. For the former, thedielectric material 205 may either serve as a substrate (e.g., largearea) upon which the LED device 208 is mounted prior to bonding with theinterposer 350 (e.g., forming the LED package 201, 202, or 203), or thedielectric material 205 may be affixed to the interposer 350 before theLED device 208 is affixed over the dielectric material 205. For thelatter, the interposer serves as the only substrate (e.g., large area)over which LED device 208 is affixed subsequent to deposition of thedielectric material 205.

In an embodiment, an LED package structure includes at least one passiveor active component disposed on the same interposer as an LED device.FIG. 3B illustrates an exemplary LED package 302 including all thefeatures illustrated in FIG. 3A with the addition of an integratedcircuit (IC) 375A disposed on the interposer 350. Thermal stress on theIC 375A is mitigated in the package structure embodiments describedherein through application of through substrate vias and thermallyisolation between the IC 375A LED device 208 provided by the low thermalconductivity dielectrics (e.g., glass) employed for the dielectricmaterial 205 and/or interposer 350.

In the exemplary embodiment, the IC 375A is an IC chip bonded to asurface of the interposer 350 (e.g., in a recess). The 375A may besurface mounted to the interposer 350, for example flip-chip bonded to aredistribution layer 370 (e.g., that may be formed on a backside of themetal film 209 prior to bonding to the interposer 350). Generally, theIC 375A is to function in some capacity related to the LED device 208and, as such, is electrically coupled to one or more of the metalpads/interconnects 215. As one example, the IC 375A is a driver orcontroller of the LED device 208 controlling one or more aspects ofoptical emission from the LED device, such as, but not limited to,emission wavelength (i.e., color) and output power. In another exemplaryembodiment, the IC 375A is a power supply, such as, but not limited, toa buck-boost regulated current source, or the like. In anotherembodiment, the IC 375A contains memory, and/or logic, and/or sensingcircuitry (e.g., ambient light detector, MEMS-based motion detector,etc.), and/or an RF transmitter and/or receiver (e.g., implementing aZigBee® protocol stack for networking the LED device 208). As such, inembodiments the LED package 302 is a purpose-built package-levelintegrated LED device with the IC 375A rendering the LED device 208independently addressable and remotely controllable. Such “smart” LEDdevices may be considered a package-level integrated display deviceswith any number of LED devices 208 controllable from a point outside ofthe package 302. As further shown in FIG. 3B, metal interconnectscomprising a redistribution layer 370 are built-up on the interposer 350using any conventional package build-up process (e.g., organicdielectrics) with a via 371 electrically coupled to an output pad of theIC 375A extending through the metal film 209 and dielectric material 205to contact the metal pad 215. In embodiments, the via 371 includes adielectric liner disposed over the inside sidewall of the via 371,separating and electrically isolating a fill metal, and/or metaldiffusion barrier, and/or metals in a catalytic material employed toplate the fill metal from the metal film 209. Generally the dielectricliner 215B may be organic or inorganic, and, for example, may be one ormore layers of at least one of: silicon dioxide (SiO₂), aluminum oxide(Al₂O₃), tantalum oxide (Ta₂O₅), silicon nitride (Si_(x)N_(y)), siliconcarbide (SiC), silicon oxy-carbo-nitride (SiOCN), a benzocyclobutene(BCB)-based polymer, or a (p-xylylene)-based polymer, such as ParyleneX.

In further embodiments, the LED device 208 is integrated with passivedevices disposed on the interposer 350. In FIG. 3B, a thin filmcapacitor 375B is electrically coupled to the metal pad 215 through theredistribution interconnect 370 and via 371. The thin film capacitor375B may have any conventional package-level capacitor structure, suchas, but not limited to a metal-insulator-metal (MIM) stack, formed withany convention package-level technique, such as printing and/or metalplating. As further illustrated in FIG. 3B, an inductor 375C is alsoformed on the interposer 350 and is integrated with the LED device 208through an electrical coupling (e.g., through the metal pad 215). One ormore such package-level capacitors, inductors, and resistors may all beintegrated with the LED device 208 with the interposer 350 to provide anintegrated substrate 210 upon which the LED device 208 is to be mounted.

For embodiments where an LED package includes passive or active (IC)components, the interposer 350 may either be bonded to theredistribution layer 370 built-up over the dielectric material 205 andthe metal film 209 (e.g., as would be formed on the LED packages 201,202 and 203), bonded to the metal film 209 (where the metal film 209 andthe dielectric material 205 is not first plated onto the interposer 350,but the redistribution layer 370 is formed on the interposer), or bondedto the dielectric material 205 (where the metal film 209 is plated overthe redistribution layer 370). In such an embodiment, the dielectricmaterial 205 may either serve as a substrate (e.g., large area) uponwhich the LED device 208 is mounted prior to bonding with the interposer350 (e.g., forming the LED package 201, 202, or 203), or the dielectricmaterial 205 may be affixed to the interposer 350 before the LED device208 is affixed over the dielectric material 205. Alternatively, each ofthe redistribution layer 370, the metal film 209, and the dielectricmaterial 205 may be deposited onto the interposer. For such anembodiment, the interposer serves as the only substrate (e.g., largearea) over which LED device 208 is affixed subsequent to deposition ofthe dielectric material 205.

In an embodiment, an LED package includes a metallized interposer with ametal film disposed on a side of the interposer opposite an LED device.FIG. 3C illustrates an exemplary LED package 303 including all thefeatures of the LED package 302 (FIG. 3B) with the addition of a backside metal 380 disposed on the interposer 350. In some embodiments, asillustrated in FIG. 3C, a thin film dielectric 379 may be disposed onthe back side of the interposer 350, between the back side metal 380 andthe interposer to improve adhesion of the back side metal 380 and/orprovide electrical isolation, for example where the interposer 350 ispolysilicon having relatively high electrical leakage properties. Theback side metal 380 is to function as a heat spreader, heat sink, or asan interface to which a heat sink may be bonded or otherwise affixed. Inone embodiment, the back side metal 380 is plated through a mask to forman integrated heat sink having greater external surface area than thesurface area of the interposer occupied by the back side metal 380.Generally, the back side metal 380 may be any of the metals describedelsewhere herein for the via metal 360. Preferred embodiments of theback side metal 380 include a nickel-tungsten alloy (NiW), or anickel-molybdenum alloy (NiMo), a cobalt-tungsten alloy (CoW), orcobalt-molybdenum alloy (CoMo). In one embodiment, the via metal 360 andthe back side metal 380 are of a same composition and may be depositedconcurrently. In a further embodiment where the metal film 209 is formedon the interposer 350 rather than on the dielectric material 205, eachof the metal film 209, via metal 360, and back side metal 380 are of asame composition and may be deposited onto the interposer concurrently.

In an embodiment, an LED package includes a surface mounted componentdisposed on the same side of the dielectric material as the LED device.FIG. 3D illustrates an exemplary LED package 304 including all thefeatures of the LED package 302 (FIG. 3B) with the addition of anintegrated circuit (IC) 385A disposed on the dielectric material 205.The exemplary LED package 304 further illustrates a passive device 385B(e.g., capacitor, inductor, resistor) mounted to the dielectric material205. The IC 385A and/or passive component 385B are electrically coupledto the LED device 208 with an output pad coupled to an electrode of theLED device 208 (e.g., out of the plane of FIG. 3D, so not depicted). Forexample, a wire bond may extend between the passive or active componentsand at least one metal pad 215. Alternatively, the IC 385A may beflip-chip bonded to have an output pad coupled to a metal pad coupled toan electrode of the LED device 208 (e.g., the metal pad 215 or anotherinterconnected to the metal pad 215). The IC 385A may be any of thedevices described in reference to the IC 375A, such as, but not limitedto a LED device driver chip, memory chip, digital logic chip (ASIC orFPGA, etc.), analog sensor chip, RF transceiver chip, or asystem-on-chip (SoC) including a functional combination of these ICs. Asfurther shown in FIG. 3D, a molding compound 388 may be disposed overcomponents mounted on the front side of the dielectric 205. The moldingcompound 388 may be any conventional in the packaging arts for theparticular component or may be of the same transparent material employedfor the cap 320 as a matter of fabrication convenience. The moldingcompound 388 may contain silica aerogel and xerogel to provide thermalisolation. In further embodiments, a first IC is disposed on theinterposer 350, for example as shown in FIG. 3C, and a second IC isdisposed on the dielectric 205, for example as shown in FIG. 3D.

The LED package structures described thus far herein may be incorporatedinto a wide variety of end user devices, such as, but not limited to,LED bulbs for general illumination (e.g., down lights, headlights,signal lamps, etc.), and special purpose displays. In the context ofspecial purpose displays, the LED package structures may serve as abacklight system (e.g., for a liquid crystal display) or may formindividual pixels of a display (e.g., in a large form LED display suchas a billboard, etc.). One advantage of these package structures is thatthe same structure can be utilized in these separate applications withwide latitude for scaling the number of LED device per package-levelunit with little or no retooling of the packaging line. For example,where one application requires only one LED device (e.g., a miniatureindicator lamp), a first LED package with no integrated ICs or passivecomponents is formed with a first plated metal pad pattern and withpackage singulation occurring at the single LED device level. A secondLED package with a plurality of LED devices may then be formed with adifferent plated metal pad pattern and with package singulationgenerating larger units having more LED devices in each unit. A thirdLED package with a plurality of LED device and an integrated IC may thenbe formed with the addition of a second bonding module. For thesevarious packages, a same R2R or panel-based packaging technique may beused.

FIG. 3E illustrates one LED display backlighting system 305 inaccordance with an embodiment. Generally, the LED display backlightingsystem 305 entails the package structure 320 (FIG. 3A) disposed on ametal chassis 390. As such, the one LED device 208 shown in FIG. 3E isan atomic unit of the backlighting system 350. As shown in FIG. 3E, aninterposer TSuV 355 includes via metal 360 extending through theinterposer 350 to be in direct contact with the metal chassis 390. Inthe exemplary embodiments where the via metal 360 has a low CTE but highthermal conductivity (e.g., comprising molybdenum or tungsten alloyssuch as NiW, NiMo, CoW, or CoMo), heat from the LED device 208 can beefficiently removed vertically to the metal chassis because theinterposer TSuV 355 has a longitudinal axis aligned with the LED device208 and the transparent dielectric material 205 is relatively thin.Thermal cross-talk between adjacent LED devices within the backlightingsystem 305 are reduced or minimized by low thermal conductivities of theinterposer 350 (glass, ceramic, etc.) and dielectric material 205. Infurther embodiments, the via metal 360 may also extend through the metalfilm 209 and/or the dielectric material 205 to make direct contact withthe LED device 208, as is shown in FIG. 3F for the backlighting system306. Where the dielectric layer 205 and/or the interposer 350 is a largearea panel (e.g., non-alkali glass, soda lime glass, parylene, aluminumoxide, or amorphous or polycrystalline silicon, etc.), the backlightingsystems 305, 306 may have a very large form factor entailing a largenumber of LED devices and interposer TSuVs or may be of a very smallform factor entailing a small population of LED devices and TSuVs.Although not depicted in FIGS. 3E and 3F, the LED backlighting systems305, 306 are to have a liquid crystal display panel disposed above theLED package of claim 1 and any such panel in the art may be utilized asembodiments of the present invention are not limited in this respect.

FIG. 4A illustrates an exploded isometric view of an LED bulb 401, inaccordance with an embodiment of the present invention. As shown, bulb401 includes a cover 420, a metal chassis 430 and a base 425. Assembledinto the chassis 430 is one or more of the LED package structuresdescribed herein. For each of the various package structure embodimentsdescribe, the substrate 210 is affixed (e.g., soldered) to the metal 430to dissipate the heat from LED devices 208 that are thermally coupledthrough thermal vias in the substrate 210. As further shown, the bulb401 includes a cluster of LED devices mounted in an array. Each LEDdevice 208 in a cluster may generate light having a white point, or eachcluster may generate light having a white point as a population of LEDdevices. Also disposed on the substrate 210 is one or more ICs 385A thatare surface mounted (e.g., as shown in FIG. 3D) or embedded into thesubstrate 210 (e.g., as shown in FIG. 3B) and having one or more of thefunctions described elsewhere herein. Any of the passive componentsdescribed elsewhere herein for the LED packages may also be integratedonto the substrate 210 in any of the manners previously described. Inone embodiment, at least a portion of the line-level power conditioningis integrated onto the substrate 210, reducing the cost of the bulb 401.In another embodiment where the IC 385A includes an RF transceiver, thebulb 401 is imparted with an independent remote control interfaceintegrated onto the substrate 210 through which function of one or moreof the LED device 208 may be modulated. For example, where the base is astandard Edison-style screw base, the bulb 401 may be retrofitted intoan existing light fixture and be independently addressable/controllablevia the IC 385A.

FIG. 4B illustrates a cross-sectional view of an LCD display 402employing the LED backlight system 305 (FIG. 3E), in accordance with anembodiment of the present invention. As shown, the LCD layers 445 areaffixed over mixing layers 440, which are in turn affixed over thebacklight system 305. FIG. 4C illustrates a plan-view of an LED display403 employing an LED package structure, in accordance with an embodimentof the present invention. The LED display 403 includes a plurality ofLED clusters 450 arrayed over the dielectric material 205. Each of theLED clusters 450 includes at least three LEDs to emit at three differentcolors (e.g., RBG) which, when combined, have a white point. Dependingon which package structure embodiment is employed, the dielectric 205may further be disposed over the interposer 350 with the metal film 209disposed there between (i.e. to form a laminate substrate 210) with aninterposer TSuV having a longitudinal axis aligned with one of theplurality of LEDs or LED clusters 450. Via fill metal is then in directcontact with the metal chassis and the LED package to thermally coupleeach LED of the plurality to the metal chassis (e.g., as illustrated inFIG. 3E). For certain such embodiments where the LED package includes anintegrated circuit (e.g., IC 375A in FIG. 3B or IC 385A in FIG. 3D), theintegrated circuit is an integrated pixel controller circuit surfacemounted onto at least one of the dielectric material and interposer. Theintegrated pixel controller circuit is electrically coupled to the LEDsin the LED clusters. Wih the LED clusters and pixel controller areintegrated onto a same substrate (e.g., dielectric material 205), noseparate means of support for integrated circuits is needed in the LEDdisplay 403 whereas a separate printed circuit board (PCB) isconventional.

FIG. 4D illustrates a functional block diagram of an LED system 404, inaccordance with an embodiment of the present invention. The variousfunctional elements of the LED system 404 are all packaged together on asame substrate or interposer. In the simplest embodiment, LED system 404includes an LED device and an LED controller 485 disposed on thetransparent dielectric material 205. In the exemplary embodimentillustrated, the LED system 404 includes the LED display 403 aspreviously described in the context of FIG. 4C. The LED display 403 iscommunicatively coupled to the LED controller 485 which is to controlthe light output of the display. In further embodiments, at least one ofa sensor 454 and RF IC 455 are also packaged with the LED display 403and LED controller 485. The sensor 454 may employ any known sensortechnology, such as but not limited to MEMs sensors, thermal diodes, orphotodetector (p-i-n) devices, etc. operable to sense an environmentalconditions external to the packaged LED system 404, such as, but notlimited to ambient light level, or ambient temperature. If present, thesensor 454 has an output pad coupled to an input pad of the LEDcontroller 485. Power to the sensor 454, if needed may also be suppliedby the LED controller 485. The RF IC 455 may implement any knownwireless transceiver technology, such as, but not limited to the Zigbee®protocol stack (e.g., 2.4-GHz IEEE 802.14.4, 2.4-GHz IEEE 802.15.4)which may further implement the Zigbee Smart Energy ProfileSpecification 0x0109 to implement a uniquely addressable nodecorresponding to the packaged LED system 404 and at least acceptcommands from external of the LED system 404 that are communicated tothe LED controller 485 and affect emissions in the LED display 403.

FIGS. 5A and 5B illustrate substrate handling techniques for fabricationof LED package structures, in accordance with embodiments. FIG. 5Aillustrates a panel handling robot 501 that may be utilized in one ofmore of the methods described herein to form one or more of the LEDpackage structures described herein. For example, where a large areapanel (e.g., glass) is employed as the dielectric material 205, thepanel handling robot 501 may be utilized to transfer the dielectricmaterial 205 through the various plating, LED device bonding, IC chipbonding, and singulation process modules to arrive at the LED packagestructures described herein. FIG. 5B illustrates a reel-to-reelprocessing line 502 that that may be utilized in one of more of themethods described herein to form one or more of the LED packagestructures described herein. For example, where a substrate (e.g.,glass) of sufficient flexibility is employed as the dielectric material205, the reel-to-reel processing line 502 may be utilized to transferthe dielectric material 205 through the various plating, LED devicebonding, IC chip bonding, and singulation process modules to arrive atthe LED package structures described herein. For example, in oneembodiment, a starting dielectric material 205 is disposed on an inputroller 510A which is fed into plating and chip bonding stations beforebeing rolled on an output roller 510B. Alternatively, a startingdielectric material 205 is disposed on the input roller 510A which isfed into plating and chip bonding stations before being singulated.

FIG. 5C illustrates a factory line 550 for fabrication of LED packagestructures, in accordance with embodiments. The factory line flow 550 isan exemplary series of processing modules or stations through which asubstrate (e.g., transparent dielectric material 205 or interposer 350)may be sequentially processed (though not necessarily in the orderdepicted). Depending on the embodiment, one or more reel-to-reelprocessing line 502 may implement one or more of each of the processingmodules depicted in FIG. 5C to assemble any of the LED packagestructures described herein.

The factory line 550 includes a via formation station 555 in which blindor through vias are formed into either the dielectric material 205 orinterposer 350. The via formation station 555 may entail a plasmaetching system, or preferably a laser which may either directly ablatematerial to form the vias, or more preferably for embodiments where thevias are formed in a glass, the laser modifies the glass to fromcolumnar regions which may be selectively wet etched to form anisotropicvias. The factory line 550 further includes a via wet clean station 560for cleaning/etching of the vias subsequent to exposing thesubstrate/interposer to plasma or laser via formation. In furtherembodiments, the via formation station is adapted for photoselectiveplating, described further elsewhere herein, in which a laser is toimplement a selective patterning of a photosensitive catalytic material.

The factory line 550 includes a via fill plating station 565. In theexemplary embodiment, the via fill plating station 565 includes anactivation station where a catalytic material may be selectivelyactivated in first portions of the substrate/interposer (e.g., within avia) relative to second portions where no catalytic material is to be(e.g., on a surface of the dielectric material 205 where no metalpad/interconnect 215 or metal film 209 is to be formed). In furtherembodiments, the via fill plating station 565 includes a catalyticmaterial removal station where catalytic material may be selectivelyremoved in second portions where no catalytic material to be (e.g., on asurface of the dielectric material 205 where no metal pad/interconnect215 or metal film 209 is to be formed) relative to first portions of thesubstrate/interposer (e.g., within a via) where catalytic material is toremain. In further embodiment, the via fill plating station 565 includesan electroless or electrolytic plating bath in which one of the via fillmetals 240 or 360 is formed.

In the exemplary embodiment, the factory line 550 includes a wetdielectric deposition station 570. The wet dielectric deposition station570 may be any station known in the art for spray or immersionapplication of one or more of dielectric materials described herein,such as, but not limited to silicon dioxide, parylenes, or alumina oxide(e.g., forming the dielectric material 205, transparent cap 230, etc.).An electrode/interconnect plating station 575 is employed in the factorline 550 where the plating of metal pads/interconnects 215, etc. is notconcurrent with the via fill. The plating station 575 may similarlyinclude an activation station where an activation layer comprisingcatalytic material is deposited. The plating station 575 may include alaser station where regions of the activation layer are exposed toselectively activate or deactivate catalytic material in the activationlayer. The plating station may further include an electroless platingbath or electrolytic plating bath to deposit any of the metalcompositions described elsewhere herein for the metal pads/interconnects215. The plating station 575 may further include a selective bumpplating station, for example where an LED device or LED devicecontroller IC is to be flip-chip bonded to the dielectric 205.

The factory line 550 concludes with a dicing station 585 where largearea substrate are singulated into individual LED package structures.Any of laser-based, mechanical saw, or anisotropic etch (DRIE)-basedscribing may be performed with mechanical sawing and laser-basedtechniques being preferable for the large area substrate embodiments(e.g., panels or reel-fed).

The factory line 550 includes a mounting station 580 where at least theLED device 208 is surface mounted to the transparent dielectric 205. Themounting station 580 may be any conventional pick and place chipmounting station, reel-to-reel or otherwise, operable to wire bond orflip-chip bond the LED device 208 to the metal pads/interconnects 215.

FIG. 6 illustrates a method 601 for fabrication of LED packagestructures, in accordance with embodiments. The methods described in thecontext of FIG. 6 may be implemented by the factory line 550.

In one embodiment where the LED package structure 301 is formed, themethod 601 begins with receiving the interposer 350. In embodimentswhere the LED package structures 302, 303 or 304 are formed, theinterposer 350 is received with the integrated circuit 375A and/orpassive device 375B mounted. An interposer TSuV is then formed atoperation 605, for example with deep reactive ion (DRIE) etching, laserablation, laser assisted removal (i.e., columnar conversion), laser jetdrilling, water jet drilling, etc.

At operation 608, the fill metal 360 is plated into the interposer TSuV.Prior to plating the fill metal 360, one or more of a dielectric liner,diffusion barrier (metal such as Ti, Ta, TiW, TiN, TaN, or dielectricsuch as Si₃N₄, etc.) may be deposited depending on the material employedfor the interposer 350. In certain embodiments the fill metal 360 andthe metal film 209 is plated concurrently at operation 608. In otherembodiments where the metal film 209 is deposited prior to forming theTSuV at operation 605, the TSuV formed at operation 605 is a blind via,and the fill metal 360 is formed by plating metal seeded from the metalfilm 209. Plating of the fill metal 360 may be selective, in which casefilling of the TSuV 355 does not result in blanket plating of at leastone of the front side or back side surfaces of the interposer 350, ornon-selective where metal is also plated on at least one of the frontside (e.g., to form the metal film 208 or back side metal 380). Infurther embodiments, where an integrated heat sink is to be formed fromthe back side metal 380, photoselective plating may be utilized topattern the back side metal 380. Applicable photoselective platingtechniques are described further below in the context of selective viafilling and selective formation of metal pads 215.

In certain selective via fill embodiments, a catalytic material is toselectively activate via surfaces only. In one such embodiment,catalytic material is deposited over a sidewall of the through TSuV 355,and over front or back side of the interposer 350. This may be done byexposing a via to a chemical activation solution (e.g. bath exposure,spin coat, spray coat, etc.). The chemical activation solution may beany known in the art for forming surfaces activated with one or more ofcatalytic materials described elsewhere herein. Where the catalyticmaterial is metal particles, the chemical activation solution hascatalytic metal species that are reduced to form metal particles on atleast the sidewalls of the TSuV 355. For such an embodiment where thecatalytic material includes palladium (Pd) particles, a palladiumactivation solution includes a source of reducible palladium species,such as, but not limited to palladium chloride. The chemical activationsolution may further include hydrochloric acid, acetic acid, andhydrofluoric acid or ammonium fluoride for contact displacementdeposition and reducing agents such as, but not limited to borohydride,hypophosphite, dimethylamine borane (DMAB), hydrazine, and formaldehydefor electroless deposition.

In other selective via fill embodiments, a photosensitive film (e.g.,titanium oxide (TiO₂), tin oxide (SnO₂), zinc oxide (ZnO), and leadiodide (PbI₂)) is deposited on the interposer 350. For such embodiments,the photosensitive film further includes catalytic particles either on atop surface of the film or embedded throughout a thickness of thephotosensitive film. In such embodiments, operation 608 entails, atleast in part, exposing the TSuV 355 to a chemical solution containing aphotosensitive species. For example an amorphous TiO₂ layer includingpalladium may be formed by spin-coating on to a workpiece a solutioncontaining a source of titanium ions and a solution containing a sourceof palladium ions. During a REDOX reaction, the oxidation state of thetitanium ion may increase while the oxidation state of the palladium isreduced with the ion becoming a metal particle. Upon drying, a driedlayer including the catalytic material within the photosensitive film isformed.

In other selective via fill embodiments, the operation 608 includesforming a polymer film with the catalytic material disposed on thesurface and/or embedded through a thickness of the polymer film. Forexample, the TSuV 355 may be exposed to a chemical solution containing apolymerizing agent which, upon drying, forms a dried layer including thecatalytic material, a polymerizing species, and may also include aphotosensitive species. In one such embodiment where the catalyticmaterial is SAM-NH₂Pd, a reduction of palladium ions in a polymerizingsolution is achieved with a reducing agent, such as, but not limited todimethylaminoborane (DMAB) or hypophoshite.

In still another selective via fill embodiment, the operation 608entails depositing a seed metal over the via sidewalls (and any barriermetal and/or dielectric liner present on the sidewall) and depositing aphotoresist over the seed metal. Generally, the seed metal may be anyknown in the art, such as but not limited to, copper (Cu), gold (Au),silver (Ag), nickel (Ni), or cobalt (Co), and wherein the fill metalcomprises least one of: copper (Cu), gold (Au), silver (Ag), nickel(Ni), cobalt (Co), tin (Sn), palladium (Pd), tungsten (W), tin-silveralloy (SnAg), tin-silver-copper alloy (SAC), indium-tin alloy (InSn),nickel-palladium-gold alloy (NiPdAu), or lead-tin alloy (SnPb). Thephotoresist is then patterned to remove the photoresist in all regionsexcept for the via. The seed metal (and barrier if present) is thenremoved in regions not protected by the photoresist followed bystripping of the photoresist. An alternative to removing the barrier, ifpresent, is oxidizing the barrier through exposure to an oxygen plasmaafter removing the photoresist and seed layer from regions not protectedby the photoresist.

Following any of these catalytic material deposition operations, thecatalytic material is removed selectively from over a region of thesubstrate adjacent to the via. The removal process is selective relativeto the via sidewall such that the catalytic material is not removed fromthe entire longitudinal length of the TSuV 355, but is however removedfrom substantially all no-via surfaces, such as over the front sideand/or back side of the interposer 350. The catalytic material mayremoved from all surfaces except for a longitudinal via length passingthrough the interposer 350.

Selective removal of the catalytic material may be performed in a numberof fashions so that no activation layer is formed on the flat (e.g.,front or back side) of the interposer 350, depending on the catalyticmaterial composition. In embodiments, at least one chemical, mechanical,and photochemical technique is applied. As one example of selectivechemical removal, a solvent of the catalytic material may be applied ina manner that prevents wetting of the inner via surface. As one exampleof selective mechanical removal, an abrading force is applied through adirectional jet of solution, flow of solution, etc. in a directionapproaching parallel to the front side surface of the interposer 355 sothat at least a portion of the inner via surfaces (i.e., sidewalls) areprotected. As another example of selective mechanical removal, a pad(e.g., a CMP pad, a wet clean scrubbing, pad, etc.) is placed in directcontact with the catalytic material disposed on the interposer 355 andmotion of the pad removes mechanically (i.e., wipes off) the catalyticmaterial from the top side relative to inner via surfaces. Lift offprocesses during chemical etching of a sacrificial material such as, butnot limited to, photoresist, BCB, titanium, and aluminum disposed on thefront side surface prior to deposition of the catalytic material can bealso used to subsequently remove the catalytic material from the topsurface selectively to inner via surfaces. As an example of aphotochemical removal, where a via is received with catalytic materialincorporated within a photosensitive film, The interposer 355 is exposedto light (e.g., a laser) having an energy (hv) sufficient to remove ordeactivate the catalytic material without exposing the entire viasidewall to the light so as to retain a portion of the catalyticmaterial within the via. For example, where palladium ions are presentin a photosensitive film containing SnO₂, photo oxidation of Sn(II) toSn(IV) under UV light leads to deactivation of the reducing agentpreventing reduction of Pd(II) ions to catalytic Pd particles on thelight exposed surface and therefore, the selective deactivation of thecatalytic material.

For non-selective via fill embodiments, or following selectiveactivation for selective via fill embodiments, operation 608 entailsplating the via fill metal from the activated or seeded surfaces. In theexemplary embodiment, the plating process includes an electrolessplating process that deposits a fill metal 360 within the TSuV 355. Ingeneral, any electroless deposition process known in the art may beemployed for a process time appropriate to fill the via to the desiredlevel. In embodiments where the metal film 209 is formed prior to viafill, an electrolytic via fill is performed with the metal film 209serving as a plating electrode.

Following via fill, method 601 continues with operation 615 where theoptically transparent dielectric material 205 is deposited over themetal film 209. Any conventional deposition process may be utilized atoperation 615, depending on the composition of the dielectric material205. In preferred embodiments, a wet dielectric deposition is performedto deposit any of the materials described elsewhere herein for thedielectric material 205.

At operation 620, the metal pads/interconnects 215 are formed on thedielectric material 205. In embodiments, at least a pair of metal padsare formed by selective plating. The selective plating may generallyentail any of the techniques described above for selective activation ofthe vias 355. However, for operation 620 selectivity is between twoadjacent regions of the dielectric material 205 and so thephotoselective embodiments previously described are advantageous withlaser treatment patterning regions of a photosensitive catalyticmaterial. For example, a photosensitive layer having catalytic particlescomprising at least one of: palladium (Pd), platinum (Pt), silver (Ag),gold (Au), nickel (Ni), cobalt (Co), or copper (Cu) may be wet depositedand regions of the photosensitive layer to exposed to light (e.g., froma laser source) having energy sufficient to modulate the activity of thecatalytic particles. The metal pads are then electrolessly plated on thepatterned regions of active catalytic material.

At operation 625, the LED device(s) 208 are mounted onto the transparentdielectric material 205 with terminals of the LED electrically coupledto the pair of electrodes. As previously described any flip-chip (e.g.,C4) process, wire bonding, or like process may be employed. The mountedLED device(s) 208 are then encapsulated with the optically transparentlens material (e.g., cap 230). Wet deposition techniques, for example,may be utilized, followed by a drying and/or curing operation.

The method 601 is then completed with singulating the interposer 350 atoperation 635. In embodiments, laser-based modification of theinterposer, laser-based ablation of the interposer, or deep reactive ionetching of the interposer is performed at operation 635. Alternatively,singulation can be by mechanical sawing.

Fabrication of the LED package structures 201 through 204 may follow amethod similar to the method 601. For example, in one embodiment, themetal for the metal pads/interconnects 215 or metal film 209 is blanketplated onto the transparent dielectric material 205 (e.g., panel or rollof glass, parylene, etc.). A wet deposition (e.g., spray, immersion,etc.) of photosensitive catalytic material is then deposited. Exemplaryphotosensitive material may again be any of: titanium oxide (TiO₂), tinoxide (SnOx), zinc oxide (ZnO), and lead iodide (PbI₂). Thephotosensitive material further includes catalytic particles, such as,but not limited to, palladium (Pd), platinum (Pt), silver (Ag), gold(Au), nickel (Ni), cobalt (Co), or copper (Cu). The photosensitivematerial is then exposed to light having an energy sufficient to createcatalytic species (e.g., for TiO₂ a positive image is formed) or toinduce chemical dissolution or deactivation of catalytic particles(e.g., for SnO₂ a negative image is formed). The pad metal 215 is thenselectively plated on the dielectric material 205. With the formation ofthe cap 230 and singulation occurring as described for the method 601.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, while flow diagrams inthe figures show a particular order of operations performed by certainembodiments of the invention, it should be understood that such order isnot required (e.g., alternative embodiments may perform the operationsin a different order, combine certain operations, overlap certainoperations, etc.). Furthermore, many other embodiments will be apparentto those of skill in the art upon reading and understanding the abovedescription. Although the present invention has been described withreference to specific exemplary embodiments, it will be recognized thatthe invention is not limited to the embodiments described, but can bepracticed with modification and alteration within the spirit and scopeof the appended claims. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A light emitting diode (LED) package, comprising: a flexible substrate including: a layer of optically transparent dielectric material comprising a first side and a second side opposite the first side; and a metal film disposed on the optically transparent dielectric material at the second side; an LED affixed to the optically transparent dielectric material at the first side; a pair of metal pads disposed on the first side of the optically transparent dielectric material and electrically coupled to terminals of the LED; and an optically transparent cap disposed over the first side of the optically transparent dielectric material encapsulating the LED.
 2. The LED package of claim 1, wherein the optically transparent dielectric material comprises a large area panel having a surface area of at least 3500 cm², wherein the LED is one of a plurality of LEDs arrayed over a first portion of the surface area on a first side of the panel; and wherein the metal film is a continuous film covering a second portion of the surface area on a second side of the panel at least as large as the first portion.
 3. The LED package of claim 1, wherein the optically transparent dielectric material comprises a non-alkali glass, soda lime glass, parylene, aluminum oxide having a thickness between 0.1 μm and 1000 μm.
 4. The LED package of claim 1, wherein the metal pads comprise at least one of aluminum (Al), silver (Ag), gold (Au), nickel (Ni), copper (Cu), silver-tungsten alloy (AgW), copper-palladium alloy (CuPd), nickel-silver (Ni—Ag), nickel-gold (Ni—Au), nickel-copper (Ni—Cu), copper-silver (Cu—Ag) bi-layer, nickel-copper-tin (Ni—Cu—Sn) or nickel-copper-silver (Ni—Cu—Al) tri-layer.
 5. The LED package of claim 1, further comprising: a through substrate via (TSuV); and a via metal disposed in the TSuV, wherein the via metal is selected from the group consisting of: copper (Cu), nickel (Ni), cobalt (Co), tungsten (W), molybdenum (Mo), aluminum (Al), and their alloys.
 6. The LED package of claim 5, wherein the via metal comprises a nickel-tungsten alloy (NiW), a nickel-molybdenum alloy (NiMo), a cobalt-tungsten (CoW), or cobalt-molybdenum (CoMo).
 7. The LED of claim 5, wherein the metal film is selected from the group consisting of: aluminum (Al), aluminum-silicon alloy (AlSi), aluminum-copper alloy (AlCu), aluminum-silicon-copper alloy (AlSiCu), silver (Ag), gold (Au), copper (Cu), chromium (Cr), a copper-silver (Cu—Ag) bi-layer stack, or nickel-copper-silver (Ni—Cu—Ag) tri-layer stack.
 8. The LED package of claim 6, wherein the TSuV has a longitudinal axis aligned with a center of the LED.
 9. The LED package of claim 1, wherein the LED terminals are flip-chip bonded to the pair of metal pads, or wherein the LED is surface mounted to the optically transparent dielectric material with the terminals wire-bonded to the metal pads, and wherein the cap comprises a plastic lens.
 10. The LED package of claim 9, wherein the transparent dielectric comprises at least one cavity with at least one LED or integrated circuit disposed in the cavity.
 11. The LED package of claim 1, further comprising: an interposer in contact with the metal film; an interposer through substrate via (TSuV); and a via metal disposed in the interposer TSuV, wherein the via metal is selected from the group consisting of: copper (Cu), nickel (Ni), cobalt (Co), tungsten (W), molybdenum (Mo), aluminum (Al), and their alloys.
 12. The LED package of claim 11, wherein the via metal comprises a nickel-tungsten alloy (NiW), or a nickel-molybdenum alloy (NiMo), a cobalt-tungsten alloy (CoW), or cobalt-molybdenum alloy (CoMo).
 13. The LED package of claim 11, wherein the interposer comprises non-alkali glass, soda lime glass, parylene, amorphous silicon, polycrystalline silicon, aluminum nitride (AlN), boronitride (BN), aluminum-oxide (Al₂O₃) having a thickness between 1 μm and 1000 μm.
 14. The LED package of claim 13, wherein the interposer TSuV does not extend beyond the metal film, wherein the interposer TSuV has a longitudinal axis aligned with a center of the LED, and wherein no interposer TSuV is disposed below the pair of metal pads.
 15. The LED package of claim 14, further comprising an integrated circuit disposed on the interposer, and wherein the LED package further comprises: a via extending through both the optically transparent dielectric material and the metal film, wherein a via metal disposed in the via is electrically isolated from the metal film and electrically contacting at least one of the pair of metal pads to an output pad of the integrated circuit.
 16. The LED package of claim 15, wherein the integrated circuit comprises at least one of a controller or power supply.
 17. The LED package of claim 14, further comprising an integrated circuit disposed on the first side of the optically transparent dielectric material, wherein the integrated circuit is surface mounted to the first side with wire bonds to at least one of the electrodes or the integrated circuit is flip-chip bonded to at least one of the pair of electrodes.
 18. A light emitting diode (LED) display backlighting system, comprising: the LED package of claim 1, further comprising a plurality of LEDs arrayed over the optically transparent dielectric material; a metal chassis; an interposer disposed between the LED package and the metal chassis; a plurality of interposer through substrate vias (TSuVs) extending through the interposer, wherein each interposer TSuV has a longitudinal axis aligned with one of the plurality of LEDs; and a via metal disposed in the interposer TSuVs, the via metal in direct contact with the metal chassis and the LED package to thermally couple each LED of the plurality to the metal chassis.
 19. The LED display backlighting system of claim 18, wherein the via metal comprises a nickel-tungsten alloy (NiW), a nickel-molybdenum alloy (NiMo), a cobalt-tungsten alloy (CoW), or cobalt-molybdenum alloy (CoMo).
 20. The LED display backlighting system of claim 18, wherein at least one of the dielectric layer and the interposer is a large area panel of non-alkali glass, soda lime glass, parylene, aluminum oxide, or amorphous or polycrystalline silicon, having a surface area of at least 3500 cm².
 21. The LED display backlighting system of claim 18, further comprising a liquid crystal display panel disposed above the LED package.
 22. The LED package of claim 1, wherein the optically transparent dielectric material is a portion of a flexible roll of dielectric film for reel to reel processing, wherein the LED is one of a plurality of LEDs arrayed over a first portion of the surface area on a first side of the dielectric film; and wherein the metal film is a continuous film covering a second portion of the surface area on a second side of the dielectric film at least as large as the first portion.
 23. A light emitting diode (LED) display, comprising: the LED package of claim 1, further comprising a plurality of LED clusters arrayed over the optically transparent dielectric material, wherein each LED cluster includes at least three LEDs operable to emit at three different colors which, when combined, have a white point; an interposer in contact with the metal film; a plurality of interposer through substrate vias (TSuVs) extending through the interposer, wherein each interposer TSuV has a longitudinal axis aligned with one LED cluster or with one of the at least three LEDs in an LED cluster; and a via metal disposed in the interposer TSuVs.
 24. The LED display of claim 23, wherein the via metal comprises a nickel-tungsten alloy (NiW), a nickel-molybdenum alloy (NiMo), a cobalt-tungsten alloy (CoW), or cobalt-molybdenum alloy (CoMo).
 25. The LED display of claim 23, wherein at least one of the transparent dielectric layer and the interposer is a large area panel of non-alkali glass, soda lime glass, amorphous or polycrystalline silicon, Al₂O₃ or AlN, having a surface area of at least 3500 cm².
 26. The LED display of claim 23, further comprising a pixel controller integrated circuit surface mounted onto at least one of the optically transparent dielectric material and interposer, wherein the pixel controller integrated circuit is electrically coupled to at least one LED in one of the LED clusters.
 27. A light emitting diode (LED) bulb, comprising: the LED package of claim 1, further comprising a plurality of LEDs arrayed over the optically transparent dielectric material, wherein the plurality of LEDs is operable to emit at a white point; an interposer in contact with the metal film; a plurality of interposer through substrate vias (TSuVs) extending through the interposer, wherein each of interposer TSuVs has a longitudinal axis aligned with one of the LEDs or aligned with a center of the plurality of LEDs; and a via metal disposed in the interposer TSuV.
 28. The light emitting diode (LED) bulb of claim 27, further comprising an LED controller integrated circuit surface mounted or flip-chip connected to the optically transparent dielectric material or interposer, the LED controller integrated circuit electrically coupled to the plurality of LEDs and isolated from the LED by a dielectric material having a thermal conductivity no greater than that of silicon dioxide.
 29. The light emitting diode (LED) bulb of claim 27, further comprising a heat sink coupled to the via metal, wherein the heat sink is of the same composition as the via metal.
 30. A light emitting diode (LED) system, comprising: a flexible substrate including: a layer of optically transparent dielectric material comprising a first side and a second side opposite the first side; and a metal film disposed on the optically transparent dielectric material at the second side; an LED controller integrated circuit surface mounted or flip-chip connected to the optically transparent dielectric material or an interposer, the LED controller integrated circuit electrically coupled to a plurality of LEDs disposed on the first side of the optically transparent dielectric material; and at least one of an RF and sensor circuit disposed on the optically transparent dielectric material or the interposer and electrically coupled with the LED controller integrated circuit. 